Fix Mixamo Root Bone

readme.md

Instructions

General Prep

1. Download the rig with animation(s) from https://mixamo.com
2. I prefer to import the FBX for each animation into an "animation library" .blend file.
3. Delete all but 1 armature and rename the actions to something human readable.

Using the Add-On/Script:

1. Put the python file into a zip for easy installation in blender
2. Edit the armature and add a bone named root. Parent the mixamorig:Hips bone to root (keep offsets)
3. Make the playback frame range include the keyframes you want captured
4. Click the Fix Root Motion Bone button and the keyframes will be edited

fix_mixamo_root.py

import bpy


bl_info = {
    "name": "Mixamo Root Fixer",
    "description": "Moves location xz from mixamo hips to root bone",
    "author": "Steven Landow",
    "version": (1, 0),
    "blender": (3, 6, 0),
    "category": "Animation",
}


class OperatorRootMotionFix(bpy.types.Operator):
    bl_idname = "stevenctl.mixamo_root_motion_fix"
    bl_label = "Fix Root Motion Bone"

    def execute(self, context):
        try:
            hip_motion_to_root()
        except Exception as e:
            self.report({"ERROR"}, e)
        return {"FINISHED"}


class RootMotionFixPanel(bpy.types.Panel):
    bl_label = "Fix Root Motion Bone"
    bl_category = "Mixamo Fix"
    bl_idname = "stevenctl.mixamo_fix_panel"

    bl_space_type = "VIEW_3D"
    bl_region_type = "UI"

    def draw(self, context):
        self.layout.operator(OperatorRootMotionFix.bl_idname)


def hip_motion_to_root():
    scene = bpy.context.scene
    if not scene:
        return
    obj = bpy.context.active_object
    if not obj or obj.type != "ARMATURE":
        print("no selected armature")
        return
    action = obj.animation_data.action
    if not action:
        print("no selected action")
        return
    if not obj.pose.bones['mixamorig:Hips']:
        print("no hips")
        return
    if not obj.pose.bones['root']:
        print("no root")
        return
    for frame in range(scene.frame_start, scene.frame_end+1):
        scene.frame_set(frame)
        root = obj.pose.bones['root']
        hips = obj.pose.bones['mixamorig:Hips']
        xz = hips.location.xz
        root.location.xz = xz
        root.keyframe_insert("location", frame=frame)
        hips.location.xz = (0, 0)
        hips.keyframe_insert("location", frame=frame)


def register():
    bpy.utils.register_class(OperatorRootMotionFix)
    bpy.utils.register_class(RootMotionFixPanel)


def unregister():
    bpy.utils.unregister_class(OperatorRootMotionFix)
    bpy.utils.unregister_class(RootMotionFixPanel)